Today when I dropped it into 4wd mode, it's making a strange growling/scraping noise coming somewhere from the area around the 2wd/4wd shifter in the floor. It only happens when it's coasting. When accelerating it gets quieter. I'm familiar with the hum coming out of a truck when it's in 4wd, and that's not it. Is it possible something might have dried up or gotten rusty underneath? It wasn't doing that a few months ago.
Any ideas?